Multilayer coil component

ABSTRACT

A multilayer coil component includes an element body, a coil disposed in the element body, and an external electrode disposed in the element body and electrically connected to the coil. The element body includes a principal surface that is a mounting surface, and an end surface positioned adjacent to the principal surface and extending in a direction crossing to the principal surface. The external electrode includes an underlying metal layer and a conductive resin layer. The underlying metal layer is formed on the principal surface and the end surface. The conductive resin layer is formed to cover the underlying metal layer. A thickness of the conductive resin layer at an end positioned above the principal surface of the underlying metal layer is equal to or greater than 50% of a maximum thickness of a portion positioned above the principal surface of the conductive resin layer.

This is a Continuation of application Ser. No. 15/598,606 filed May 18,2017, which in turn claims priority to Japanese Application No.2016-107490 filed May 30, 2016, Japanese Application No. 2016-107491filed May 30, 2016, and Japanese Application No. 2016-107493 filed May30, 2016. The entire disclosures of the prior applications are herebyincorporated by reference herein their entirety.

TECHNICAL FIELD

The present invention relates to a multilayer coil component.

BACKGROUND

Japanese Patent No. 5172818 discloses an electronic component. Thiselectronic component includes an element body and an external electrodedisposed on the element body. The external electrode includes anunderlying metal layer and a conductive resin layer. The underlyingmetal layer is formed on the element body. The conductive resin layer isformed to cover the underlying metal layer.

SUMMARY

In the case where an electric component is a multilayer coil component,a problem described below may occur. A conductive resin layer generallyincludes metal powders and resin (for example, thermosetting resin).Therefore, a resistance of a conductive resin layer is higher than aresistance of an underlying metal layer including metal. Therefore, whenan external electrode includes a conductive resin layer, a DC resistanceof a multilayer coil component may increase.

To suppress that a DC resistance of a multilayer coil componentincreases, it is considered that a thickness of a conductive resin layeris reduced. When the thickness of the conductive resin layer is small, aresistance of the conductive resin layer is low as compared with whenthe thickness of the conductive resin layer is large. However, when thethickness of the conductive resin layer is small, a stress relaxationeffect by the conductive resin layer may be reduced as compared withwhen the thickness of the conductive resin layer is large.

An object of a first aspect of the present invention is to provide amultilayer coil component with a low DC resistance even when an externalelectrode includes a conductive resin layer.

An object of a second aspect of the present invention is to provide amultilayer coil component in which deterioration in a stress relaxationeffect by a conductive resin layer is suppressed even if a thickness ofthe conductive resin layer is small.

A multilayer coil component is expected to suppress degradation ofelectrical characteristics even in the case where a crack is generatedin an element body.

An object of a third aspect of the present invention is to provide amultilayer coil component in which degradation of electricalcharacteristics is suppressed even in the case where a crack isgenerated in an element body.

A multilayer coil component according to the first aspect includes anelement body, a coil disposed in the element body, an external electrodedisposed on the element body, and a connection conductor disposed in theelement body. The connection conductor includes one end connected to thecoil and another end connected to the external electrode. The elementbody includes a principal surface that is a mounding surface and an endsurface. The end surface is positioned adjacent to the principal surfaceand extends in a direction crossing to the principal surface. Theexternal electrode includes a underlying metal layer and a conductiveresin layer. The underlying metal layer is formed on the principalsurface and the end surface. The conductive resin layer is formed tocover the underlying metal layer. The other end of the connectionconductor is exposed at the end surface and connected to the underlyingmetal layer. When viewed from a direction orthogonal to the end surface,a position where the other end of the connection conductor on the endsurface is exposed at the end surface differs from a position where athickness of a portion positioned above the end surface of theconductive resin layer is maximum.

As a result of research and study by inventors of the present invention,matters described below have been revealed. An underlying metal layergenerally includes a sintered metal layer. The sintered metal layer is alayer formed by sintering metal components (metal powders) included in aconductive paste. Therefore, the sintered metal layer is hardly formedas a uniform metal layer, and it is difficult to control a shape of thesintered metal layer. The sintered metal layer, for example, sometimeshas a shape (such as a mesh shape) including a plurality of openings(through holes).

A conductive resin layer is a layer in which metal powders are dispersedin cured resin. A current path is formed in the conductive resin layerwhen the metal powders come into contact with each other. It isdifficult to control the dispersion state of the metal powders in theresin. Therefore, a position of the current path in the conductive resinlayer is not easily controlled.

Accordingly, current paths on the conductive resin layer and theunderlying metal layer differ depending on products. In some products,for example, metal powders are formed in lines at a position where athickness of a portion positioned above an end surface of the conductiveresin layer is maximum, and the metal powders and a underlying metallayer having a mesh shape come into contact with each other.Hereinafter, the position where the thickness of the portion positionedabove the end surface of the conductive resin layer is maximum is called“the maximum thickness position of the conductive resin layer”. In thisproduct, when viewed from a direction orthogonal to an end surface, if aposition where another end of a connection conductor on the end surfaceis exposed and the maximum thickness position of the conductive resinlayer coincide, a current flows into the other end of the connectionconductor through a current path formed at the maximum thicknessposition of the conductive resin layer. Therefore, a DC resistance ishigh. To obtain a product with a low DC resistance, even if a currentpath is formed at the maximum thickness position of the conductive resinlayer, a probability that a current flows in the current path should bereduced.

In a multilayer coil component according to the first aspect, whenviewed from the direction orthogonal to an end surface, a position wherethe other end of the connection conductor is exposed at the end surfaceand the maximum thickness position of the conductive resin layer aredifferent. Therefore, it is highly possible that a current flows to theother end of the connection conductor through a current path formed at aposition other than the maximum thickness position of the conductiveresin layer. As a result, the multilayer coil component with a high DCresistance is not easily obtained. In other words, it is possible tolower a DC resistance of the multilayer coil component.

A multilayer coil component according to the second aspect includes anelement body, a coil disposed in the element body, and an externalelectrode disposed on the element body. The external electrode iselectrically connected to the coil. The element body includes aprincipal surface that is a mounding surface and an end surface. The endsurface is positioned adjacent to the principal surface and extends in adirection crossing to the principal surface. The external electrodeincludes an underlying metal layer and a conductive resin layer. Theunderlying metal layer is formed on the principal surface and the endsurface. The conductive resin layer is formed to cover the underlyingmetal layer. A thickness of the conductive resin layer at an endpositioned above the principal surface of the underlying metal layer isequal to or greater than 50% of a maximum thickness of a portionpositioned above the principal surface of the conductive resin layer.

As a result of research and study by inventors of the present invention,matters described below have been revealed. For example, when amultilayer coil component is mounted on an electronic device (forexample, a circuit board or an electronic component), an external forceacting on the multilayer coil component from the electronic device actsas a stress force on an element body through an external electrode insome cases. The stress force tends to concentrate on an end of theunderlying metal layer positioned above the principal surface that is amounting surface. Therefore, a crack starting from the end of theunderlying metal layer may be generated in the element body.

In the multilayer coil component according to the second aspect, thethickness of the conductive resin layer at the end positioned above theprincipal surface of the underlying metal layer is equal to or greaterthan 50% of the maximum thickness of the portion positioned above theprincipal surface of the conductive resin layer. Therefore, even in thecase where an external force acts on the multilayer coil component, astress force does not easily concentrate on the end of the underlyingmetal layer, and a crack is hardly caused from the end. Therefore, inthe multilayer coil component according to the second aspect, even if athickness of the conductive resin layer is small, deterioration in astress relaxation effect by the conductive resin layer is suppressed.

A multilayer coil component according to the third aspect includes anelement body, a coil disposed in the element body, and an externalelectrode disposed on the element body. The external electrode iselectrically connected to the coil. The element body includes aprincipal surface that is a mounding surface and an end surface. The endsurface is positioned adjacent to the principal surface and extends in adirection crossing to the principal surface. The external electrodeincludes an underlying metal layer and a conductive resin layer. Theunderlying metal layer is formed on the principal surface and the endsurface. The conductive resin layer is formed to cover the underlyingmetal layer. An end positioned above the principal surface of theunderlying metal layer is positioned on an outer side of the coil whenviewed from a direction orthogonal to the principal surface.

In the multilayer coil component according to the third aspect, even inthe case where a crack starting from the end of the underlying metal isgenerated in the element body, the generated crack hardly reaches thecoil since the end of the underlying metal layer is positioned on theouter side of the coil when viewed from the direction orthogonal to theprincipal surface. Therefore, even in the case where a crack isgenerated in the element body, the crack hardly affects the coil, anddegradation of electrical characteristics of the multilayer coilcomponent is suppressed.

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not to beconsidered as limiting the present invention.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a multilayer coil componentaccording to an embodiment;

FIG. 2 is a diagram for illustrating a cross-sectional configuration ofa multilayer coil component according to the embodiment;

FIG. 3 is a perspective view illustrating a configuration of a coilconductor;

FIG. 4 is a diagram for illustrating a cross-sectional configuration ofan external electrode;

FIG. 5 is a diagram for illustrating a cross-sectional configuration ofan external electrode;

FIG. 6 is a plan view of an element body on which a first electrodelayer is formed;

FIG. 7 is a plan view of a second electrode layer included in anelectrode portion positioned on an end surface; and

FIG. 8 is a plan view of a second electrode layer included in anelectrode portion positioned on an end surface.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. In the followingdescription, the same elements or elements having the same functions aredenoted with the same reference numerals and overlapped explanation isomitted.

With reference to FIGS. 1 to 3, a configuration of a multilayer coilcomponent 1 according to the embodiment will be described. FIG. 1 is aperspective view illustrating a multilayer coil component according tothe embodiment. FIG. 2 is a diagram for illustrating a cross-sectionalconfiguration of a multilayer coil component according to theembodiment. FIG. 3 is a perspective view illustrating a configuration ofa coil conductor;

As illustrated in FIG. 1, the multilayer coil component 1 includes anelement body 2 and a pair of external electrodes 4 and 5. Therectangular parallelepiped shape includes a shape of a rectangularparallelepiped in which a corner portion and a ridge portion arechamfered and a shape of a rectangular parallelepiped in which a cornerportion and a ridge portion are rounded. The external electrode 4 isdisposed on one end side of the element body 2. The external electrode 5is disposed on another end side of the element body 2. The externalelectrodes 4 and 5 are separated each other. The multilayer coilcomponent 1 is applied to, for example, a bead inductor or a powerinductor.

The element body 2 includes a pair of end surfaces 2 a and 2 b opposingeach other, a pair of principal surfaces 2 c and 2 d opposing eachother, and a pair of side surfaces 2 e and 2 f opposing each other. Theend surfaces 2 a and 2 b are positioned adjacent to the principalsurfaces 2 c and 2 d. The end surfaces 2 a and 2 b are also positionedadjacent to the side surfaces 2 e and 2 f. The principal surface 2 c or2 d is a mounting surface. For example, when the multilayer coilcomponent 1 is mounted on an electronic device which is not illustrated(for example, a circuit board or an electronic component), the mountingsurface is a surface opposing the electronic device.

In the embodiment, a direction in which the end surfaces 2 a and 2 boppose each other (a first direction D1) is a length direction of theelement body 2. A direction in which the principal surfaces 2 c and 2 doppose each other (a second direction D2) is a height direction of theelement body 2. A direction in which the side surfaces 2 e and 2 foppose each other (a third direction D3) is a width direction of theelement body 2. The first direction D1, the second direction D2, and thethird direction D3 are mutually orthogonal.

A length in the first direction D1 of the element body 2 is longer thana length in the second direction D2 of the element body 2 and alsolonger than a length in the third direction D3 of the element body 2.The length in the second direction D2 of the element body 2 and thelength in the third direction D3 of the element body 2 are equal. Inother words, in the embodiment, the end surfaces 2 a and 2 b have asquare shape, and the principal surfaces 2 c and 2 d and the sidesurfaces 2 e and 2 f have a rectangle shape. The lengths of the firstdirection D1, the second direction D2, and the third direction D3 of theelement body 2 may be equal. The lengths of the second direction D2 andthe third direction D3 of the element body 2 may be different.

It is noted herein that the term “equal” does not always mean thatvalues are exactly equal. The values may also be said to be equal incases where the values have a slight difference within a predeterminedrange or include a manufacturing error or the like. For example, when aplurality of values fall within the range of ±5% of an average of theplurality of values, the plurality of values may be defined to be equal.

Each of the end surfaces 2 a and 2 b extends in the second direction D2to couple the principal surfaces 2 c and 2 d. Each of the end surfaces 2a and 2 b extends in a direction crossing to the principal surfaces 2 cand 2 d. Each of the end surfaces 2 a and 2 b also extends in the thirddirection D3. The principal surfaces 2 c and 2 d extend in the firstdirection D1 to couple the end surfaces 2 a and 2 b. The principalsurfaces 2 c and 2 d also extend in the third direction D3. The sidesurfaces 2 e and 2 f extend in the second direction D2 to couple theprincipal surfaces 2 c and 2 d. The side surfaces 2 e and 2 f extend inthe first direction D1.

The element body 2 is constituted of a plurality of insulator layers 6(refer to FIG. 3) laminated. Each of the insulator layers 6 is laminatedin the direction in which the principal surfaces 2 c and 2 d oppose eachother. A lamination direction of each insulator layer 6 coincides withthe direction in which the principal surfaces 2 c and 2 d oppose eachother. The direction in which the principal surfaces 2 c and 2 d opposeeach other is also called “the lamination direction”. Each of theinsulator layers 6 has a substantially rectangular shape. In the elementbody 2 in practice, each of the insulator layers 6 is integrated in sucha manner that a boundary between the insulator layers 6 cannot bevisually recognized.

Each of the insulator layers 6 includes a sintered ceramic green sheetincluding a ferrite material (for example, a Ni—Cu—Zn based ferritematerial, a Ni—Cu—Zn—Mg based ferrite material, or a Ni—Cu based ferritematerial). In other words, the element body 2 includes a ferritesintered body.

The multilayer coil component 1 includes a coil 15 disposed in theelement body 2. As illustrated in FIG. 3, the coil 15 includes aplurality of coil conductors (a plurality of internal conductors) 16 a,16 b, 16 c, 16 d, 16 e, and 16 f. A plurality of the coil conductors 16a to 16 f includes a conductive material (for example, Ag or Pd). Aplurality of the coil conductors 16 a to 16 f is a sintered body of aconductive paste including a conductive material (for example, Agpowders or Pd powders).

The coil conductor 16 a includes a connection conductor 17 (conductor).The connection conductor 17 is disposed in the element body 2. Theconnection conductor 17 is disposed close to the end surface 2 b. Theconnection conductor 17 includes an end exposed at the end surface 2 b.The end of the connection conductor 17 is exposed at a position closerto the principal surface 2 c than a central region of the end surface 2b when viewed from a direction orthogonal to the end surface 2 b. Thecoil conductor 16 a is connected to an external electrode 5 at the endof the connection conductor 17. The coil conductor 16 a is electricallyconnected to the external electrode 5 through the connection conductor17. In the embodiment, a conductor pattern of the coil conductor 16 aand a conductor pattern of the connection conductor 17 are integrallyconnected.

The coil conductor 16 f includes a connection conductor 18 (conductor).The connection conductor 18 is disposed in the element body 2. Theconnection conductor 18 is disposed close to the end surface 2 a. Theconnection conductor 18 includes an end exposed at the end surface 2 a.The end of the connection conductor 18 is exposed at a position closerto the principal surface 2 d than a central region of the end surface 2a when viewed from a direction orthogonal to the end surface 2 a. Thecoil conductor 16 f is connected to the external electrode 4 at the endof the connection conductor 18. The coil conductor 16 f is electricallyconnected to the external electrode 4 through the connection conductor18. In the embodiment, a conductor pattern of the coil conductor 16 fand a conductor pattern of the connection conductor 18 are integrallyconnected.

A plurality of coil conductors 16 a to 16 f is juxtaposed in thelamination direction of the insulator layer 6 in the element body 2. Aplurality of the coil conductors 16 a to 16 f is arranged in an order ofthe coil conductor 16 a, the coil conductor 16 b, the coil conductor 16c, the coil conductor 16 d, the coil conductor 16 e, and the coilconductor 16 f from a side near the outermost layer. In the embodiment,the coil 15 includes a portion other than the connection conductor 17 inthe coil conductor 16 a, a plurality of the coil conductors 16 b to 16d, and a portion other than the connection conductor 18 in the coilconductor 16 f.

Ends of the coil conductors 16 a to 16 f are connected each other bythrough-hole conductors 19 a to 19 e. The coil conductors 16 a to 16 fare mutually electrically connected by the through-hole conductors 19 ato 19 e. The coil 15 includes the coil conductors 16 a to 16 felectrically connected to each other. Each of the through-holeconductors 19 a to 19 e includes a conductive material (for example, Agor Pd). As with a plurality of the coil conductors 16 a to 16 f, each ofthe through-hole conductors 19 a to 19 e is a sintered body of aconducive paste including a conductive material (for example, Ag powdersor Pd powders).

The external electrode 4 is positioned at an end on the end surface 2 aside in the element body 2 when viewed in the first direction D1. Theexternal electrode 4 includes an electrode portion 4 a positioned on theend surface 2 a, an electrode portion 4 b positioned on the principalsurfaces 2 c and 2 d, and an electrode portion 4 c positioned on theside surfaces 2 e and 2 f. The external electrode 4 is formed on thefive surfaces 2 a, 2 c, 2 d, 2 e, and 2 f.

The electrode portions 4 a, 4 b, and 4 c adjacent to each other areconnected on a ridge line portion of the element body 2. The electrodeportions 4 a, 4 b, and 4 c are mutually electrically connected. Theelectrode portions 4 a and 4 b are connected on a ridge line portionbetween the end surface 2 a and each of the principal surfaces 2 c and 2d. The electrode portions 4 a and 4 c are connected on a ridge lineportion between the end surface 2 a and each of the side surfaces 2 eand 2 f.

The electrode portion 4 a is disposed to cover the entire end exposed atthe end surface 2 a of the connection conductor 18. The connectionconductor 18 is directly connected to the external electrode 4. Theconnection conductor 18 connects the coil conductor 16 a (one end of thecoil 15) and the electrode portion 4 a. The coil 15 is electricallyconnected to the external electrode 4.

The external electrode 5 is positioned at an end on the end surface 2 bside in the element body 2 when viewed in the first direction D1. Theexternal electrode 5 includes an electrode portion 5 a positioned on theend surface 2 b, an electrode portion 5 b positioned on the principalsurfaces 2 c and 2 d, and an electrode portion 5 c positioned on theside surfaces 2 e and 2 f. The external electrode 5 is formed on thefive surfaces 2 b, 2 c, 2 d, 2 e, and 2 f.

The electrode portions 5 a, 5 b, and 5 c adjacent to each other areconnected on a ridge line portion of the element body 2. The electrodeportions 5 a, 5 b, and 5 c are mutually electrically connected. Theelectrode portions 5 a and 5 b are connected on a ridge line portionbetween the end surface 2 b and each of the principal surfaces 2 c and 2d. The electrode portions 5 a and 5 c are connected on a ridge lineportion between the end surface 2 b and each of the side surfaces 2 e,and 2 f.

The electrode portion 5 a is disposed to cover the entire end exposed atthe end surface 2 b of the connection conductor 17. The connectionconductor 17 is directly connected to the external electrode 5. Theconnection conductor 17 connects the coil conductor 16 f (another end ofthe coil 15) and the electrode portion 5 a. The coil 15 is electricallyconnected to the external electrode 5.

As illustrated in FIGS. 4 and 5, each of the external electrodes 4 and 5includes a first electrode layer 21, a second electrode layer 23, athird electrode layer 25, and a fourth electrode layer 27. Each of theelectrode portions 4 a, 4 b, and 4 c includes the first electrode layer21, the second electrode layer 23, the third electrode layer 25, and thefourth electrode layer 27. Each of the electrode portions 5 a, 5 b, and5 c includes the first electrode layer 21, the second electrode layer23, the third electrode layer 25, and the fourth electrode layer 27. Thefourth electrode layer 27 includes an outermost layer of the externalelectrodes 4 and 5. FIGS. 4 and 5 are diagrams for illustrating across-sectional configuration of an external electrode.

The first electrode layer 21 is formed by applying and sintering aconductive paste on a surface of the element body 2. The first electrodelayer 21 is a sintered metal layer formed by sintering metal components(metal powders) included in a conductive paste. In other words, thefirst electrode layer 21 is a sintered metal layer formed on the elementbody 2. In the embodiment, the first electrode layer 21 is a sinteredmetal layer including Ag. The first electrode layer 21 may be a sinteredmetal layer including Pd. The first electrode layer 21 includes Ag orPd. In the conductive paste, for example, a glass component, an organicbinder, and an organic solvent are mixed in powders including Ag or Pd.

The second electrode layer 23 is formed by curing a conductive resinapplied on the first electrode layer 21. The second electrode layer 23is formed to cover a whole of the first electrode layer 21. The firstelectrode layer 21 is an underlying metal layer to form the secondelectrode layer 23. The second electrode layer 23 is a conductive resinlayer formed on the first electrode layer 21. For example, athermosetting resin, metal powders, and an organic solvent are mixed inthe conductive resin. For example, Ag powders are used in the metalpowders. For example, a phenol resin, an acrylic resin, a siliconeresin, an epoxy resin, or a polyimide resin is used in the thermosettingresin.

The third electrode layer 25 is formed by a plating method on the secondelectrode layer 23. In the embodiment, the third electrode layer 25 is aNi plated layer formed by Ni plating on the second electrode layer 23.The third electrode layer 25 may be a Sn plated layer, a Cu platedlayer, or an Au plated layer. The third electrode layer 25 includes Ni,Sn, Cu, or Au.

The fourth electrode layer 27 is formed by a plating method on the thirdelectrode layer 25. In the embodiment, the fourth electrode layer 27 isa Sn plated layer formed by Sn plating on the third electrode layer 25.The fourth electrode layer 27 may be a Cu plated layer or an Au platedlayer. The fourth electrode layer 27 includes Sn, Cu, or Au. The thirdelectrode layer 25 and the fourth electrode layer 27 constitute a platedlayer formed on the second electrode layer 23. In the embodiment, theplated layer formed on the second electrode layer 23 has a two-layerstructure.

Each first electrode layer 21 includes a first portion 21 a positionedabove the end surfaces 2 a and 2 b. The first portion 21 a correspondsto the first electrode layer 21 included in the electrode portions 4 aand 5 a. An average thickness of the first portion 21 a is, for example,10 to 30 μm. A thickness of the first portion 21 a is, as illustrated inFIGS. 4 and 5, reduced at both ends in the second direction D2 andincreased in an intermediate portion between the both ends. Each secondelectrode layer 23 includes a first portion 23 a positioned above theend surfaces 2 a and 2 b. The first portion 23 a corresponds to thesecond electrode layer 23 included in the electrode portions 4 a and 5a. An average thickness of the first portion 23 a is, for example, 30 to50 μm. A thickness of the first portion 23 a is, as illustrated in FIG.4, reduced at both ends in the second direction D2 and increased in anintermediate portion between the both ends. Each third electrode layer25 includes a first portion 25 a positioned above the end surfaces 2 aand 2 b. The first portion 25 a corresponds to the third electrode layer25 included in the electrode portions 4 a and 5 a. An average thicknessof the first portion 25 a is, for example, 1 to 3 μm. Each fourthelectrode layer 27 includes a first portion 27 a positioned above theend surfaces 2 a and 2 b. The first portion 27 a corresponds to thefourth electrode layer 27 included in the electrode portions 4 a and 5a. An average thickness of the first portion 27 a is, for example, 2 to7 μm. An average thickness of a portion positioned above the endsurfaces 2 a and 2 b of the plated layer (the third and fourth electrodelayers 25 and 27) is, for example, 3 to 10 μm. The average thickness ofthe portion positioned above the end surfaces 2 a and 2 b of the platedlayer is the average thickness of the plated layer included in theelectrode portions 4 a and 5 a.

Each first electrode layer 21 includes a second portion 21 b positionedabove the principal surfaces 2 c and 2 d. The second portion 21 bcorresponds to the first electrode layer 21 included in the electrodeportions 4 b and 5 b. An average thickness of the second portion 21 bis, for example, 1 to 2 μm. A thickness of the second portion 21 b is,as illustrated in FIGS. 4 and 5, reduced at both ends in the firstdirection D1 and increased in an intermediate portion between the bothends. Each second electrode layer 23 includes a second portion 23 bpositioned above the principal surfaces 2 c and 2 d. The second portion23 b corresponds to the second electrode layer 23 included in theelectrode portions 4 b and 5 b. An average thickness of the secondportion 23 b is, for example, 10 to 30 μm. A thickness of the secondportion 23 b is, as illustrated in FIGS. 4 and 5, reduced at both endsin the first direction D1 and increased in an intermediate portionbetween the both ends. Each third electrode layer 25 includes a secondportion 25 b positioned above the principal surfaces 2 c and 2 d. Thesecond portion 25 b corresponds to the third electrode layer 25 includedin the electrode portions 4 b and 5 b. An average thickness of thesecond portion 25 b is, for example, 1 to 3 μm. Each fourth electrodelayer 27 includes a second portion 27 b positioned above the principalsurfaces 2 c and 2 d. The second portion 27 b corresponds to the fourthelectrode layer 27 included in the electrode portions 4 b and 5 b. Anaverage thickness of the second portion 27 b is, for example, 2 to 7 μm.An average thickness of a portion positioned above the principalsurfaces 2 c and 2 d of the plated layer (the third and fourth electrodelayers 25 and 27) is, for example, 3 to 10 μm. The average thickness ofthe portion positioned above the principal surfaces 2 c and 2 d of theplated layer is the average thickness of the plated layer included inthe electrode portions 4 b and 5 b. An average thickness of the secondelectrode layer 23 included in the electrode portions 4 b and 5 b isequal to or less than 15 times of an average thickness of the firstelectrode layer 21 included in the electrode portions 4 b and 5 b. Theaverage thickness of the second electrode layer 23 included in theelectrode portions 4 b and 5 b is equal to or less than 5 times of theaverage thickness of a plated layer included in the electrode portions 4b and 5 b.

The average thickness is calculated, for example, in the followingmanner.

A sectional view including each of the first portions 21 a, 23 a, 25 a,and 27 a of the first electrode layer 21, the second electrode layer 23,the third electrode layer 25, and the fourth electrode layer 27 isobtained. The sectional view is, for example, a sectional view of thefirst electrode layer 21, the second electrode layer 23, the thirdelectrode layer 25, and the fourth electrode layer 27 in the case wherethe layers are cut at a plane in parallel with a pair of surfaces (forexample a pair of the side surfaces 2 e and 2 f) opposing each other andpositioned at an equal distance from a pair of the surfaces. On theobtained sectional view, each area of the first portions 21 a, 23 a, 25a, and 27 a of the first electrode layer 21, the second electrode layer23, the third electrode layer 25, and the fourth electrode layer 27 iscalculated.

A quotient obtained by dividing an area of the first portion 21 a of thefirst electrode layer 21 by a length of the first portion 21 a on theobtained sectional surface indicates an average thickness of the firstportion 21 a of the first electrode layer 21. A quotient obtained bydividing an area of the first portion 23 a of the second electrode layer23 by a length of the first portion 23 a on the obtained sectionalsurface indicates an average thickness of the first portion 23 a of thesecond electrode layer 23. A quotient obtained by dividing an area ofthe first portion 25 a of the third electrode layer 25 by a length ofthe first portion 25 a on the obtained sectional surface indicates anaverage thickness of the first portion 25 a of the third electrode layer25. A quotient obtained by dividing an area of the first portion 27 a ofthe fourth electrode layer 27 by a length of the first portion 27 a onthe obtained sectional surface indicates an average thickness of thefirst portion 27 a of the fourth electrode layer 27.

A sectional view including each of the second portions 21 b, 23 b, 25 b,and 27 b of the first electrode layer 21, the second electrode layer 23,the third electrode layer 25, and the fourth electrode layer 27 isobtained. The sectional view is, for example, a sectional view of thefirst electrode layer 21, the second electrode layer 23, the thirdelectrode layer 25, and the fourth electrode layer 27 in the case wherethe layers are cut at a plane in parallel with a pair of surfaces (forexample a pair of the side surfaces 2 e and 2 f) opposing each other andpositioned at an equal distance from a pair of the surfaces. On theobtained sectional view, each area of the second portions 21 b, 23 b, 25b, and 27 b of the first electrode layer 21, the second electrode layer23, the third electrode layer 25, and the fourth electrode layer 27 iscalculated.

A quotient obtained by dividing an area of the second portion 21 b ofthe first electrode layer 21 by a length of the second portion 21 b onthe obtained sectional surface indicates an average thickness of thesecond portion 21 b of the first electrode layer 21. A quotient obtainedby dividing an area of the second portion 23 b of the second electrodelayer 23 by a length of the second portion 23 b on the obtainedsectional surface indicates an average thickness of the second portion23 b of the second electrode layer 23. A quotient obtained by dividingan area of the second portion 25 b of the third electrode layer 25 by alength of the second portion 25 b on the obtained sectional surfaceindicates an average thickness of the second portion 25 b of the thirdelectrode layer 25. A quotient obtained by dividing an area of thesecond portion 27 b of the fourth electrode layer 27 by a length of thesecond portion 27 b on the obtained sectional surface indicates anaverage thickness of the second portion 27 b of the fourth electrodelayer 27.

A plurality of sectional views may be obtained, and each of thequotients for each sectional view may be obtained. In which case, anaverage value of a plurality of the obtained quotients may be an averagethickness.

Next, a relation between the first electrode layers 21 and secondelectrode layers 23 of the external electrodes 4 and 5 above theprincipal surfaces 2 c and 2 d will be described with reference to FIGS.4 and 5.

Each first electrode layer 21 includes a first end 21 e positioned abovethe principal surfaces 2 c and 2 d. A thickness T_(RS1) of the secondportion 23 b of the second electrode layer 23 at a position of the firstend 21 e is equal to or greater than 50% of a maximum thicknessT_(RSmax) of the second portion 23 b. In other words, the thicknessT_(RS1) of the second electrode layer 23 positioned above the first end21 e of the first electrode layer 21 included in the electrode portions4 b and 5 b is equal to or greater than 50% of a maximum thicknessT_(RSmax) of the second electrode layer 23 included in the electrodeportions 4 b and 5 b. The maximum thickness T_(RSmax) is, for example,11 to 40 pin. The thickness T_(RS1) is, for example, 6 to 40 pin. In theembodiment, the maximum thickness T_(RSmax) is 30 pin, and the thicknessT_(RS1) is 20 pin. In other words, the thickness T_(RS1) isapproximately 67% of the maximum thickness T_(RSmax).

In the electrode portion 4 b, the first end 21 e of the first electrodelayer 21 is positioned closer to the end surface 2 a than a positionwhere a thickness of the second portion 23 b is the maximum thicknessT_(RSmax) when viewed from a direction orthogonal to the principalsurfaces 2 c and 2 d (the second direction D2). In other words, thefirst end 21 e of the first electrode layer 21 included in the electrodeportion 4 b is positioned closer to the end surface 2 a than a positionwhere a thickness of the second electrode layer 23 included in theelectrode portion 4 b is the maximum thickness T_(RSmax) when viewedfrom the second direction D2. When a plane including the end surface 2 ais set to a reference surface DP₁, a length L_(SE1) in the firstdirection D1 from the reference surface DP₁ to the first end 21 e isshorter than a length L_(RS1) in the first direction D1 from thereference surface DP₁ to a position where a thickness of the secondelectrode layer 23 included in the electrode portion 4 b is the maximumthickness T_(RSmax).

In the electrode portion 5 b, the first end 21 e of the first electrodelayer 21 is positioned closer to the end surface 2 b than a positionwhere a thickness of the second portion 23 b is the maximum thicknessT_(RSmax) when viewed from the second direction D2. In other words, thefirst end 21 e of the first electrode layer 21 included in the electrodeportion 5 b is positioned closer to the end surface 2 b than a positionwhere a thickness of the second electrode layer 23 included in theelectrode portion 5 b is the maximum thickness T_(RSmax) when viewedfrom the second direction D2. When a plane including the end surface 2 bis set to a reference surface DP₂, a length L_(SE2) in the firstdirection D1 from the reference surface DP₂ to the first end 21 e isshorter than a length L_(RS2) in the first direction D1 from thereference surface DP₂ to a position where a thickness of the secondelectrode layer 23 included in the electrode portion 5 b is the maximumthickness T_(RSmax).

The length L_(SE1) is, for example, 80 μm. The length L_(RS1) is, forexample, 120 μm. The length L_(SE2) is, for example, 80 μm. The lengthL_(RS2) is, for example, 120 μm. In the embodiment, the length L_(SE1)and the length L_(SE2) are equal. However, the length L_(SE1) and thelength L_(SE2) may be different. In the embodiment, the length L_(RS1)and the length L_(RS2) are equal. However, the length L_(RS1) and thelength L_(RS2) may be different.

A relation between the first electrode layers 21 and second electrodelayers 23 of the external electrodes 4 and 5 above the side surfaces 2 eand 2 f will be described next although it is not illustrated.

Each second electrode layer 23 includes a third portion positioned abovethe side surfaces 2 e and 2 f. Each first electrode layer 21 includes asecond end positioned above the side surfaces 2 e and 2 f. A thicknessof the third portion of the second electrode layer 23 at a position ofthe second end of the first electrode layer 21 is equal to or greaterthan 50% of a maximum thickness in the third portion of the secondelectrode layer 23. In other words, the thickness of the secondelectrode layer 23 positioned above the second end of the firstelectrode layer 21 included in the electrode portions 4 c and 5 c isequal to or greater than 50% of the maximum thickness of the secondelectrode layer 23 included in the electrode portions 4 c and 5 c. Thethickness of the second electrode layer 23 positioned above the secondend of the first electrode layer 21 included in the electrode portions 4c and 5 c is equal to the thickness T_(RS1). The maximum thickness ofthe second electrode layer 23 included in the electrode portions 4 c and5 c is equal to the maximum thickness T_(RSmax).

In the electrode portion 4 c, the second end of the first electrodelayer 21 is positioned closer to the end surface 2 a than a positionwhere a thickness of the third portion of the second electrode layer 23is maximum when viewed from a direction orthogonal to the side surfaces2 e and 2 f (the third direction D3). In other words, the second end ofthe first electrode layer 21 included in the electrode portion 4 c ispositioned closer to the end surface 2 a than the position where thethickness of the second electrode layer 23 included in the electrodeportion 4 c is maximum when viewed from the third direction D3.

A length in the first direction D1 from the reference surface DP₁ to thesecond end of the first electrode layer 21 included in the electrodeportion 4 c is equal to the length L_(SE1). A length in the firstdirection D1 from the reference surface DP₁ to the position where thethickness of the second electrode layer 23 included in the electrodeportion 4 c is maximum is equal to the length L_(RS1). Therefore, thelength in the first direction D1 from the reference surface DP₁ to thesecond end of the first electrode layer 21 included in the electrodeportion 4 c is shorter than the length in the first direction D1 fromthe reference surface DP₁ to the position where the thickness of thesecond electrode layer 23 included in the electrode portion 4 c ismaximum.

In the electrode portion 5 c, the second end of the first electrodelayer 21 is positioned closer to the end surface 2 b than a positionwhere a thickness of the third portion of the second electrode layer 23is maximum when viewed from the third direction D3. In other words, thesecond end of the first electrode layer 21 included in the electrodeportion 5 c is positioned closer to the end surface 2 b than theposition where the thickness of the second electrode layer 23 includedin the electrode portion 5 c is maximum when viewed from the thirddirection D3.

A length in the first direction D1 from the reference surface DP₂ to thesecond end of the first electrode layer 21 included in the electrodeportion 5 c is equal to the length L_(SE2). A length in the firstdirection D1 from the reference surface DP₂ to the position where thethickness of the second electrode layer 23 included in the electrodeportion 5 c is maximum is equal to the length L_(RS2). Therefore, thelength in the first direction D1 from the reference surface DP₂ to thesecond end of the first electrode layer 21 included in the electrodeportion 5 c is shorter than the length in the first direction D1 fromthe reference surface DP₂ to the position where the thickness of thesecond electrode layer 23 included in the electrode portion 5 c ismaximum.

Next, a relation between the coil 15 and the first electrode layer 21will be described with reference to FIG. 6. FIG. 6 is a plan view of anelement body on which a first electrode layer is formed;

As illustrated in FIG. 6, the first end 21 e of the first electrodelayer 21 (an end of the first electrode layer 21 included in theelectrode portions 4 b and 5 b) is positioned on an outer side of thecoil 15 when viewed from the direction orthogonal to the principalsurfaces 2 c and 2 d (the second direction D2). The first end 21 e ofthe first electrode layer 21 corresponds to an end of the firstelectrode layer 21 included in the electrode portions 4 b and 5 b. Inother words, the first electrode layer 21 included in the electrodeportions 4 b and 5 b does not overlap the coil 15 when viewed from thedirection orthogonal to the principal surfaces 2 c and 2 d. The lengthL_(SE1) is shorter than a length in the first direction D1 from thereference surface DP₁ to the coil 15. The length L_(SE2) is shorter thana length in the first direction D1 from the reference surface DP₂ to thecoil 15 in the first direction D1. A part of the first electrode layer21 included in the electrode portions 4 b and 5 b overlaps theconnection conductors 17 and 18 when viewed from the second directionD2.

The second end of the first electrode layer 21 (an end of the firstelectrode layer 21 included in the electrode portions 4 c and 5 c) isalso positioned on the outer side of the coil 15 when viewed from thethird direction D3 (the direction orthogonal to the side surfaces 2 eand 2 f) although it is not illustrated. In other words, the firstelectrode layer 21 included in the electrode portions 4 c and 5 c doesnot overlap the coil 15 when viewed from the third direction D3. A partof the first electrode layer 21 included in the electrode portions 4 cand 5 c overlaps the connection conductors 17 and 18 when viewed fromthe third direction D3.

Next, a relation between the coil 15 and the first electrode layer 21will be described with reference to FIGS. 7 and 8. FIGS. 7 and 8 areplan views of a second electrode layer including an electrode portionpositioned on an end surface.

As illustrated in FIGS. 4 and 5, the connection conductor 17 includesone end connected to the coil 15 and another end connected to the firstelectrode layer 21. The other end of the connection conductor 17 isexposed at the end surface 2 b. The connection conductor 18 includes oneend connected to the coil 15 and another end connected to the firstelectrode layer 21. The other end of the connection conductor 18 isexposed at the end surface 2 a.

When the second electrode layer 23 is formed, a conductive resin isgenerally applied by a dipping method. In which case, a thickness of thesecond electrode layer 23 included in the electrode portions 4 a and 5 ais maximized at a position corresponding to the central region of theend surfaces 2 a and 2 b and reduced as a distance from the positioncorresponding to the central region is increased, when viewed from thedirection orthogonal to the end surfaces 2 a and 2 b.

As illustrated in FIG. 7, the other end of the connection conductor 17is exposed at a position closer to the principal surface 2 c than thecentral region of the end surface 2 b when viewed from the directionorthogonal to the end surface 2 b. In other words, when viewed from thedirection orthogonal to the end surface 2 b, the position where theother end of the connection conductor 17 is exposed at the end surface 2b and a position where the thickness of the second electrode layer 23included in the electrode portion 5 a is maximum are different.

As illustrated in FIG. 8, the other end of the connection conductor 18is exposed at a position closer to the principal surface 2 d than thecentral region of the end surface 2 a when viewed from the directionorthogonal to the end surface 2 a. In other words, when viewed from thedirection orthogonal to the end surface 2 a, a position where the otherend of the connection conductor 18 is exposed at the end surface 2 a anda position where the thickness of the second electrode layer 23 includedin the electrode portion 4 a is maximum are different.

When the multilayer coil component 1 is mounted in the electronicdevice, an external force acting on the multilayer coil component 1 fromthe electronic device acts as a stress force on the element body 2through the external electrodes 4 and 5 in some cases. The stress forcetends to concentrate on the first end 21 e of the first electrode layer21 included in the electrode portions 4 b and 5 b.

In the multilayer coil component 1, the thickness T_(RS1) of the secondelectrode layer 23 positioned above the first end 21 e of the firstelectrode layer 21 included in the electrode portions 4 b and 5 b isequal to or greater than 50% of the maximum thickness T_(RSmax) of thesecond electrode layer 23 included in the electrode portions 4 b and 5b. Therefore, in the case where an external force acts on the multilayercoil component 1, a stress force hardly concentrates on the first end 21e of the first electrode layer 21 included in the electrode portions 4 band 5 b, and a crack is hardly caused from the first end 21 e of thefirst electrode layer 21 included in the electrode portions 4 b and 5 b.Therefore, in the multilayer coil component 1, even if the thickness ofthe second electrode layer 23 is small, deterioration in a stressrelaxation effect by the second electrode layer 23 is suppressed.

A ratio of the thickness T_(RS1) with respect to the maximum thicknessT_(RSmax) and a ratio of the lengths L_(SE1) and L_(SE2) with respect tothe lengths L_(RS1) and L_(RS2), which can suppress the deterioration ina stress relaxation effect will be described in detail.

Inventors of the present invention had the following tests to clarify aratio of the thickness T_(RS1) with respect to the maximum thicknessT_(RSmax) which can suppress the deterioration in a stress relaxationeffect. First, a plurality of multilayer coil components (samples S1 toS5) having different ratios of the thickness T_(RS1) with respect to themaximum thickness T_(RSmax) is prepared, and a bending strength test isperformed to each of the samples S1 to S5. After the bending strengthtest, the multilayer coil component is cut with a board to be describedlater, and it is visually confirmed whether a crack is generated in anelement body of the multilayer coil component.

In the bending strength test, first, a multilayer coil component issolder-mounted on a center of the board (a glass epoxy board). A size ofthe board is 100 mm×40 mm, and a thickness of the board is 1.6 mm Next,the board is placed on two bars parallely disposed at an interval of 90mm. The board is placed in such a manner that a surface on which themultilayer coil component is mounted faces downward. Then, a bendingstress force is applied at the center of the board from a back surfaceof the surface on which the multilayer coil component is mounted in sucha manner that a bending amount of the board reaches a desired value.

A ratio of the thickness T_(RS1) with respect to the maximum thicknessT_(RSmax) can be changed by changing the lengths L_(SE1) and L_(SE2).For example, if the first electrode layer 21 is formed in such a mannerthat the lengths L_(SE1) and L_(SE2) match the lengths L_(RS1) andL_(RS2), the thickness T_(RS1) is coincident with the maximum thicknessT_(RSmax). In which case, the ratio of the thickness T_(RS1) withrespect to the maximum thickness T_(RSmax) is 100%.

The samples S1 to S5 have the same configuration other than that ratiosof the thickness T_(RS1) with respect to the maximum thickness T_(RSmax)(ratios of the lengths L_(SE1) and L_(SE2) with respect to the lengthsL_(RS1) and L_(RS2)) are different. In each of the samples S1 to S5, alength in the first direction D1 of the element body 2 is 1.46 mm, alength in the second direction D2 of the element body 2 is 0.75 mm, anda length in the third direction D3 of the element body 2 is 0.75 mm.

In the sample S1, a ratio of the thickness T_(RS1) with respect to themaximum thickness T_(RSmax) is “40%”. A ratio of the lengths L_(SE1) andL_(SE2) with respect to the lengths L_(RS1) and L_(RS2) is “0.2”. Themaximum thickness T_(RSmax) is 30 μm, and the thickness T_(RS1) is 12μm. The lengths L_(RS1) and L_(RS2) are 120 μm, and the lengths L_(SE1)and L_(SE2) are 24 μm.

In the sample S2, a ratio of the thickness T_(RS1) with respect to themaximum thickness T_(RSmax) is “50%”. A ratio of the lengths L_(SE1) andL_(SE2) with respect to the lengths L_(RS1) and L_(RS2) is “0.6”. Themaximum thickness T_(RSmax) is 30 μm, and the thickness T_(RS1) is 15μm. The lengths L_(RS1) and L_(RS2) are 120 μm, and the lengths L_(SE1)and L_(SE2) are 72 μm.

In the sample S3, a ratio of the thickness T_(RS1) with respect to themaximum thickness T_(RSmax) is “100%”. A ratio of the lengths L_(SE1)and L_(SE2) with respect to the lengths L_(RS1) and L_(RS2) is “1.0”.The maximum thickness T_(RSmax) is 30 pin, and the thickness T_(RS1) is30 μm. The lengths L_(RS1) and L_(RS2) are 120 pin, and the lengthsL_(SE1) and L_(SE2) are 120 μm.

In the sample S4, a ratio of the thickness T_(RS1) with respect to themaximum thickness T_(RSmax) is “50%”. A ratio of the lengths L_(SE1) andL_(SE2) with respect to the lengths L_(RS1) and L_(RS2) is “1.6”. Themaximum thickness T_(RSmax) is 30 pin, and the thickness T_(RS1) is 15μm. The lengths L_(RS1) and L_(RS2) are 120 μm, and the lengths L_(SE1)and L_(SE2) are 192 μm.

In the sample S5, a ratio of the thickness T_(RS1) with respect to themaximum thickness T_(RSmax) is “40%”. A ratio of the lengths L_(SE1) andL_(SE2) with respect to the lengths L_(RS1) and L_(RS2) is “1.8”. Themaximum thickness T_(RSmax) is 30 μm, and the thickness T_(RS1) is 12μm. The lengths L_(RS1) and L_(RS2) are 120 μm, and the lengths L_(SE1)and L_(SE2) are 216 μm.

When the bending stress force is applied on the board in such a mannerthat the bending amount of the board becomes “5.0 mm”, cracks wereconfirmed on element bodies of the samples S1 and S5. In contrast,cracks were not confirmed on element bodies of the samples S2, S3, andS4.

When the bending stress force is applied on the board in such a mannerthat the bending amount of the board becomes “7.0 mm”, cracks wereconfirmed on element bodies of the samples S1, S4, and S5. In contrast,cracks were not confirmed on element bodies of the samples S2 and S3.

As described above, when the ratio of the thickness T_(RS1) with respectto the maximum thickness T_(RSmax) is equal to or greater than 50%, thedeterioration in the stress relaxation effect is suppressed. Further,when the ratio of the lengths L_(SE1) and L_(SE2) with respect to thelengths L_(RS1) and L_(RS2) is in the range of 0.6 to 1.0, thedeterioration in the stress relaxation effect is further suppressed.

The first end 21 e of the first electrode layer 21 included in theelectrode portions 4 b and 5 b is positioned on the outer side of thecoil 15 when viewed from the second direction D2. Consequently, even inthe case where a stress force concentrates on the first end 21 e of thefirst electrode layer 21 included in the electrode portions 4 b and 5 b,and a crack starting from the first end 21 e is generated in the elementbody, the crack hardly reaches the coil 15. Therefore, even in the casewhere the crack is generated in the element body 2, the crack hardlyaffects the coil 15, and degradation of electrical characteristics ofthe multilayer coil component 1 is suppressed.

A stress force hardly concentrates on an end of the second electrodelayer 23 included in the electrode portions 4 b and 5 b as compared withthe first end 21 e of the first electrode layer 21 included in theelectrode portions 4 b and 5 b. Therefore, the end of the secondelectrode layer 23 included in the electrode portions 4 b and 5 b mayoverlap the coil 15 when viewed from the second direction D2.

The first electrode layer 21 includes a sintered metal layer. Thesintered metal layer is a layer formed by sintering metal components(metal powders) included in a conductive paste. Therefore, the sinteredmetal layer is hardly formed as a uniform metal layer, and it isdifficult to control a shape of the layer. The sintered metal layer, forexample, has a shape (such as a mesh shape) including a plurality ofopenings (through holes).

The second electrode layer 23 is a layer on which metal powders aredispersed in a cured resin. A current path is formed in the secondelectrode layer 23 when the metal powders come into contact with eachother. It is difficult to control the dispersion state of the metalpowders in the resin and difficult to control a position of the currentpath in the second electrode layer 23.

Accordingly, current paths in the second electrode layer 23 and thefirst electrode layer 21 differ depending on products. In some products,for example, metal powders are formed in lines at a position where thethickness of the second electrode layer 23 included in the electrodeportions 4 a and 5 a is maximum, and the metal powders and the firstelectrode layer 21 having a mesh shape come into contact with eachother. In this product, when viewed from the first direction D1, if aposition where the other ends of the connection conductors 17 and 18 areexposed at the end surfaces 2 b and 2 a is coincident with a positionwhere a thickness of the second electrode layer 23 included in theelectrode portions 4 a and 5 a is maximum, a DC resistance increasessince a current flows into the other ends of the connection conductors17 and 18 through a current path formed at the position where thethickness of the second electrode layer 23 included in the electrodeportions 4 a and 5 a is maximum. To obtain a product with a low DCresistance, even if a current path is formed at the position where thethickness of the second electrode layer 23 included in the electrodeportions 4 a and 5 a is maximum, a provability that a current flows inthe current path should be reduced.

In the multilayer coil component 1, when viewed from the first directionD1, the position where the other ends of the connection conductors 17and 18 are exposed at the end surfaces 2 b and 2 a differs from theposition where the thickness of the second electrode layer 23 includedin the electrode portions 4 a and 5 a is maximum. Therefore, it ishighly possible that a current flows to the other ends of the connectionconductors 17 and 18 through a current path formed at a position otherthan the positon where the thickness position of the second electrodelayer 23 included in the electrode portions 4 a and 5 a is maximum.Therefore, according to the embodiment, it is difficult to obtain themultilayer coil component 1 with a high DC resistance. In other words,according to the embodiment, it is possible to lower a DC resistance ofthe multilayer coil component 1.

The first end 21 e of the first electrode layer 21 included in theelectrode portion 4 b is positioned closer to the end surface 2 a thanthe position where the thickness of the second electrode layer 23included in the electrode portion 4 b is the maximum thickness T_(RSmax)when viewed from the second direction D2. In which case, as comparedwith the case where the first end 21 e of the first electrode layer 21included in the electrode portion 4 b is positioned further away fromthe end surface 2 a than a position where the thickness of the secondelectrode layer 23 included in the electrode portion 4 b is the maximumthickness T_(RSmax), the first end 21 e of the first electrode layer 21included in the electrode portion 4 b is positioned away from the coil15.

The first end 21 e of the first electrode layer 21 included in theelectrode portion 5 b is positioned closer to the end surface 2 b thanthe position where the thickness of the second electrode layer 23included in the electrode portion 5 b is the maximum thickness T_(RSmax)when viewed from the second direction D2. In this case, as compared withthe case where the first end 21 e of the first electrode layer 21included in the electrode portion 5 b is positioned further away fromthe end surface 2 b than a position where the thickness of the secondelectrode layer 23 included in the electrode portion 5 b is the maximumthickness T_(RSmax), the first end 21 e of the first electrode layer 21included in the electrode portion 5 b is positioned away from the coil15.

Since the first end 21 e of the first electrode layer 21 included in theelectrode portions 4 b and 5 b is positioned away from the coil 15, evenin the case where a crack starting from the first end 21 e of the firstelectrode layer 21 included in the electrode portions 4 b and 5 b isgenerated in the element body 2, the crack hardly reaches the coil 15.Therefore, even in the case where a crack is generated in the elementbody 2, the crack hardly affects the coil 15, and degradation ofelectrical characteristics of the multilayer coil component 1 issuppressed.

The various embodiments have been described. However, the presentinvention is not limited to the embodiments and various changes,modifications, and applications can be made without departing from thegist of the present invention.

In the embodiment, the external electrodes 4 and 5 include the electrodeportions 4 a and 5 a, the electrode portions 4 b and 5 b, and theelectrode portions 4 c and 5 c has been described. However, a shape ofthe external electrode is not limited thereto. For example, the externalelectrode 4 may be formed only on the end surface 2 a and one principalsurface 2 c, and the external electrode 5 may be formed only on the endsurface 2 b and another principal surface 2 c. In which case, theprincipal surface 2 c is a mounting surface.

Even in the case where the thickness T_(RS1) of the second electrodelayer 23 positioned above the first end 21 e of the first electrodelayer 21 included in the electrode portions 4 b and 5 b is equal to orgreater than 50% of the maximum thickness T_(RSmax) of the secondelectrode layer 23 included in the electrode portions 4 b and 5 b, thelengths L_(SE1) and L_(SE2) may be equal to or longer than the lengthsL_(RS1) and L_(RS2). From a viewpoint of suppressing the degradation ofthe electrical characteristics of the multilayer coil component 1, asdescribed above, the lengths L_(SE1) and L_(SE2) may be shorter than thelengths L_(RS1) and L_(RS2).

The thickness T_(RS1) may be less than 50% of the maximum thicknessT_(RSmax). From a viewpoint of suppressing the deterioration in thestress relaxation effect of the multilayer coil component 1, asdescribed above, the thickness T_(RS1) may be equal to or greater than50% of the maximum thickness T_(RSmax).

The first end 21 e of the first electrode layer 21 included in theelectrode portions 4 b and 5 b may overlap the coil 15 when viewed fromthe second direction D2. From a viewpoint of suppressing the degradationof the electrical characteristics of the multilayer coil component 1, asdescribed above, the first end 21 e of the first electrode layer 21included in the electrode portions 4 b and 5 b may be positioned on theouter side of the coil 15 when viewed from the second direction D2.

When viewed from the first direction D1, a position where the other endsof the connection conductors 17 and 18 on the end surfaces 2 a and 2 bare exposed may overlap the position where the thickness of the secondelectrode layer 23 included in the electrode portions 4 a and 5 a ismaximum. Since it is difficult to obtain the multilayer coil component 1with a high DC resistance, as described above, when viewed from thefirst direction D1, the position where the other ends of the connectionconductors 17 and 18 are exposed at the end surfaces 2 b and 2 a maydiffer from the position where the thickness of the second electrodelayer 23 included in the electrode portions 4 a and 5 a is maximum.

What is claimed is:
 1. A multilayer coil component, comprising: anelement body; a coil disposed in the element body; an external electrodedisposed on the element body; a connection conductor including one endconnected to the coil and another end connected to the externalelectrode, the connection conductor being disposed in the element body,wherein the element body includes a principal surface that is a mountingsurface; and an end surface positioned adjacent to the principal surfaceand extending in a direction crossing to the principal surface, and theexternal electrode includes an underlying metal layer formed on theprincipal surface and the end surface; and a conductive resin layerformed to cover the underlying metal layer, the other end of theconnection conductor is exposed at the end surface and connected to theunderlying metal layer, and when viewed from a direction orthogonal tothe end surface, a position where the other end of the connectionconductor is exposed at the end surface differs from a position where athickness of a portion positioned above the end surface of theconductive resin layer is maximum.
 2. The multilayer coil componentaccording to claim 1, wherein an end positioned above the principalsurface of the underlying metal layer is positioned on an outer side ofthe coil when viewed from the direction orthogonal to the principalsurface.
 3. The multilayer coil component according to claim 2, whereinthe end of the underlying metal layer is positioned closer to the endsurface than a position where a thickness of the portion positionedabove the principal surface of the conductive resin layer is maximum,when viewed from the direction orthogonal to the principal surface.